1. Field of the Invention
The present invention relates to a liquid jet apparatus for ejecting liquid drops from nozzle openings of a liquid jet head to an object to be processed.
2. Description of the Related Art
As a typical example of a conventional liquid jet apparatus, there is an ink jet recording apparatus having an ink jet recording head for recording images. As other liquid jet apparatus, for example, an apparatus having a color material jet head used for manufacturing color filters of liquid crystal displays, an apparatus having an electrode material (conductive paste) jet head used for forming electrodes of organic EL displays and face emission displays (FED), an apparatus having a biological organic substance jet head used for manufacturing biological chips, and an apparatus having a sample jet head as a precise pipette may be cited.
An ink jet recording apparatus as a typical example of the liquid jet apparatus has been recently used in many printings including color printings because printing noise is comparatively low and small dots can be produced highly densely.
Such an ink jet recording apparatus generally has an ink jet recording head loaded on a carriage and moving back and forth in the width direction (head scanning direction) of recording media (an object to be processed) such as recording paper and a feed mechanism for moving recording media in the direction (feed direction) perpendicular to the head scanning direction and further has a platen which is arranged opposite to the recording head, supports recording media to be fed by the feed mechanism from the back side, and positions recording media with respect to the recording head.
The ink jet recording apparatus prints by ejecting ink drops onto recording media by the recording head in correspondence with print data. And, the recording head loaded on the carriage can eject ink in various colors, for example, black, yellow, cyan, and magenta, thus not only text printing can be realized by black ink but also full-color printing can be realized by changing the ejection rate of each ink.
When the overall surface of each recording medium is to be printed free of blanks on the edges of the recording medium (so-called xe2x80x9cfour-side edge-free printingxe2x80x9d) by the ink jet recording apparatus, in consideration of an allowance for displacements of the recording medium and the carriage, an area slightly wider than the size of the recording medium is printed.
Namely, the surface is printed free of blanks on the left and right edges (edges in the feed direction) of the recording medium, so that the scanning range of the recording head during printing can be set wider so as to extend beyond the side edges of the recording medium.
Furthermore, when the surface is to be printed free of blanks on the front and rear edges (edges in the head scanning direction) of the recording medium, at the start time of printing the recording medium, up to an area extending beyond the front edge of the recording medium is designated as an area to be printed and also at the end time of printing the recording medium, up to an area extending beyond the rear edge of the recording medium is designated as an area to be printed.
And, ink drops ejected into the areas beyond the recording medium are absorbed by an absorption member (sponge, etc.) arranged on the rear side of the recording medium opposite to the recording head.
As mentioned above, when the surface is to be printed free of blanks on the edges of the recording medium, ink drops are ejected in areas extending front and rear or left and right from the edges of the recording medium, thereby a problem arises that an ink mist moved on the rear side of the recording medium is attached to the rear edge of the recording medium and soils the recording medium. Particularly, there are problems imposed in a case of printing on both sides of recording media and a case of printing recording media both sides of which are to be used such as postal cards. Further, there are problems imposed in that misted ink soils the inside of the apparatus, and an ink mist is attached to the electric circuit and linear scale, thereby causes malfunctions, and an ink mist is deposited on the ink cartridge, and a user""s hand may be soiled.
Further, generally, the feed mechanism for feeding a recording medium in the feed direction has rollers arranged opposite to each other so as to hold and feed the recording medium. One of the rollers arranged opposite to each other is a drive roller having a structure that alumina is baked on the surface of a metallic roller so as to improve the frictional force and the other roller is a follower roller made of plastics.
And, generally, by contact and separation of these rollers with a recording medium, rubbing with the next recording medium when recording media are fed from an auto-sheet feeder, or contact of each recording medium with the structure member in the feed path, each recording medium is charged at the point of time when it is fed into the printing area. And, when recording media are charged like this, an ink mist is easily attached to the rear of each recording medium.
In order to solve these problems, a method for installing a discharging unit such as a discharging brush for discharging charged recording media may be considered. In this case, the discharging unit is installed inevitably on the downstream side of the feed mechanism composed of a pair of rollers in the feed direction, thus the distance from the feed mechanism to the printing area is made longer. Therefore, problems of deterioration of the feed precision of recording media and rising of recording media are easily caused. Further, another problem arises that paper powder is generated due to rubbing recording media such as paper by the discharging brush and attached to the nozzle, causing deterioration of the ejection performance of ink drops.
Further, in order to satisfy the recent request of high image quality, the size of ink drops ejected from the recording head is becoming smaller increasingly. Ink drops in a small size slow down suddenly due to the viscosity resistance of air, so that ink drops ejected into an area outside a recording medium from the recording head may be misted without reaching the absorption member.
The present invention has been developed with the foregoing in view and is intended to provide a liquid jet apparatus capable of preventing liquid drops ejected from a liquid jet head into an area outside an object to be processed from misting.
Especially, the present invention is intended to provide, even when liquid drops are to be fed free of blanks on the edges of an object to be processed, a liquid jet apparatus capable of preventing a liquid mist from attaching to the rear edge of the object to be processed.
A liquid jet apparatus according to the first aspect of the present invention comprises: a liquid jet head having a nozzle plate with a nozzle opening, said liquid jet head being configured to eject liquid drops from said nozzle opening by changing pressure of liquid in a pressure chamber interconnecting to said nozzle opening, a scanning mechanism configured to scan said liquid jet head in a head scanning direction, a feed mechanism configured to feed an object to be processed, to which liquid drops ejected from said liquid jet head are applied, in a feed direction perpendicular to said head scanning direction, an absorption member arranged in an area, which is on a rear side of said object to be processed under processing and opposite to said liquid jet head, and configured to absorb liquid drops ejected into an area outside said object to be processed, and a potential difference generation unit configured to generate a potential difference between at least one of said absorption member and a member neighboring said absorption member and said nozzle plate.
Preferably, said potential difference generation unit applies a voltage to at least one of said absorption member and said member neighboring said absorption member and grounds said nozzle plate.
Preferably, said potential difference generation unit grounds at least one of said absorption member and said member neighboring said absorption member and applies a voltage to said nozzle plate.
Preferably, said member neighboring said absorption member has a conductive part extended in said head scanning direction and a conductive part extended in said feed direction.
Preferably, said member neighboring said absorption member is formed in a lattice shape.
Preferably, said absorption member includes a conductive material.
Preferably, said absorption member is formed by mixing a conductive material in polyethylene or polyurethane and foaming the same.
Preferably, said absorption member is formed by plating a foam material of polyethylene or polyurethane with a conductive material.
Preferably, said absorption member contains an electrolytic liquid.
Preferably, said electrolytic liquid is a liquid ejected from said liquid jet head.
Preferably, the liquid jet apparatus further comprises a holding unit configured to hold said object to be processed under processing in an electrically isolated state.
Preferably, said holding unit has an insulating material installed at least on a surface of each member making contact with said object to be processed under processing.
Preferably, the liquid jet apparatus further comprises: a platen arranged opposite to said liquid jet head so as to support said object to be processed, which is fed by said feed mechanism, from a rear of said article and position said object to be processed with respect to said liquid jet head, wherein said absorption member is installed in said platen.
According to the liquid jet apparatus by the first aspect of the present invention, a potential difference is generated between at least one of an absorption member and a member neighboring to the absorption member and a nozzle plate by a potential difference generation unit, thus Coulomb force is acted on charged liquid drops ejected from a nozzle opening toward the absorption member, so that liquid drops ejected from the liquid jet head into an area outside an object to be processed can be surely prevented from misting.
A liquid jet apparatus according to the second aspect of the present invention comprises: a liquid jet head configured to eject liquid drops from a nozzle opening by changing pressure of liquid in a pressure chamber interconnecting to said nozzle opening, a scanning mechanism configured to scan said liquid jet head in a head scanning direction, a feed mechanism configured to feed an object to be processed, to which liquid drops ejected from said liquid jet head are given, in a feed direction perpendicular to said head scanning direction, and a liquid drop acquisition electrode arranged in an area, which is on a rear side of said object to be processed under processing and opposite to said liquid jet head, and configured to acquire liquid drops ejected into an area outside an edge of said object to be processed by electrostatic force.
Preferably, a liquid jet apparatus further comprises: a platen arranged opposite to said liquid jet head so as to support said object to be processed, which is fed by said feed mechanism, from a rear of said article and position said object to be processed with respect to said liquid jet head, said platen having an absorption member configured to absorb liquid drops ejected from said liquid jet head, wherein said liquid drop acquisition electrode is arranged in a neighborhood of said absorption member.
Preferably, said liquid drop acquisition electrode has a part extended in said head scanning direction and a part extended in said feed direction.
Preferably, said liquid drop acquisition electrode is composed of a metallic wire member.
Preferably, said liquid drop acquisition electrode is composed of a long and narrow metallic member having a triangular section.
Preferably, said liquid drop acquisition electrode is composed of a metallic needle member.
Preferably, a surface of said liquid drop acquisition electrode is treated with an insulation.
Preferably, a surface of said liquid drop acquisition electrode is treated with a corrosion preventive.
Preferably, the liquid jet apparatus according to claim 14, further comprises: a platen arranged opposite to said liquid jet head so as to support said object to be processed, which is fed by said feed mechanism, from a rear of said article and position said object to be processed with respect to said liquid jet head, said platen having an absorption member configured to absorb liquid drops ejected from said liquid jet head, wherein said absorption member is said liquid drop acquisition electrode.
Preferably, the liquid jet apparatus further comprises: a charging unit configured to charge said object to be processed.
Preferably, said charging unit has a corona discharger or a charging brush.
Preferably, said feed mechanism has a roller configured to feed said object to be processed onto said platen, and wherein said charging unit has a roller cleaner for cleaning a surface of said roller.
Preferably, the liquid jet apparatus further comprises: a voltage application unit configured to apply a high voltage to said object to be processed and hold said object to be processed at a high potential.
Preferably, said liquid drop acquisition electrode is grounded.
Preferably, the liquid jet apparatus further comprises: a voltage application unit configured to apply a high voltage to said liquid drop acquisition electrode and hold said liquid drop acquisition electrode at a high potential.
Preferably, the liquid jet apparatus further comprises a discharging unit configured to discharge static electricity from said object to be processed and installed on a downstream side of said liquid jet head in said feed direction.
Preferably, said discharging unit has a discharging brush.
Preferably, said discharging brush is in contact with a rear of said object to be processed.
According to the liquid jet apparatus by the second aspect of the present invention, liquid drops ejected into an area outside the edges of an object to be processed can be attracted and acquired by a liquid drop acquisition electrode, so that even when liquid drops are to be fed without leaving blanks on the edges of the object to be processed, a liquid mist can be prevented from attaching to the rear edge of the object to be processed.
A liquid jet apparatus according to the third aspect of the present invention comprises: a liquid jet head configured to eject liquid drops from a nozzle opening by changing pressure of liquid in a pressure chamber interconnecting to said nozzle opening, a scanning mechanism configured to scan said liquid jet head in a head scanning direction, a feed mechanism configured to feed an object to be processed, to which liquid drops ejected from said liquid jet head are given, in a feed direction perpendicular to said head scanning direction, a static electricity charging member arranged in an area which is on a rear side of said object to be processed under processing and opposite to said liquid jet head, and a static electricity generation member configured to generate static electricity by dynamically making contact with said static electricity charging member.
Preferably, the liquid jet apparatus further comprises: a platen arranged opposite to said liquid jet head so as to support said object to be processed, which is fed by said feed mechanism, from a rear of said article and position said object to be processed with respect to said liquid jet head, said platen having an absorption member configured to absorb liquid drops ejected from said liquid jet head, wherein at least a part of said static electricity charging member is arranged in the neighborhood of said absorption member.
Preferably, said platen has a liquid exhaust port.
Preferably, said platen has a liquid exhaust groove.
Preferably, said static electricity charging member is formed in a tubular shape, and wherein said static electricity generation member is arranged inside said static electricity charging member and driven and rotated around a revolving axis parallel with a tubular axis of the static electricity charging member.
Preferably, said static electricity generation member has a rotatable brush configured to dynamically make contact with an inner peripheral surface of said tubular static electricity charging member, and wherein said brush has a sectional shape of a central angle of less than or equal to 180xc2x0 around said revolving axis.
Preferably, said brush is positioned and stopped on a far side from said liquid jet head during a liquid jetting operation and is rotated when said liquid jetting operation is not performed.
Preferably, said static electricity charging member is formed by a sheet-like member curved convexly toward said liquid jet head, and wherein said static electricity generation member is arranged on a rear side of said static electricity charging member viewed from a position of said liquid jet head.
Preferably, said static electricity generation member has a rotatable brush configured to dynamically make contact by rotation with a rear of said static electricity charging member composed of said sheet-like member, and wherein said brush has a sectional shape of a central angle of less than or equal to 180xc2x0 around said revolving axis.
Preferably, said brush is positioned on a far side from said liquid jet head during a liquid jetting operation and stopped in a non-contact state with said static electricity charging member and is rotated when said liquid jetting operation is not performed.
Preferably, said static electricity charging member is formed by a sheet-like member, wherein said absorption member is arranged on a liquid jet head side of said static electricity charging member, and said static electricity generation member is arranged on a rear side of said static electricity charging member viewed from said liquid jet head.
Preferably, said static electricity generation member has a rotatable brush configured to dynamically make contact by rotation with a rear of said static electricity charging member composed of said sheet-like member, and wherein said brush has a sectional shape of a central angle of less than or equal to 180xc2x0 around-said revolving axis.
Preferably, said brush is positioned on a far side from said liquid jet head during a liquid jetting operation and stopped in a non-contact state with said static electricity charging member, and said brush is rotated when said liquid jetting operation is not performed.
Preferably, said static electricity generation member is positioned and stopped on a far side from said liquid jet head during a liquid jetting operation, and said static electricity generation member dynamically makes contact with said static electricity charging member when said liquid jetting operation is not performed.
Preferably, during said liquid jetting operation, said static electricity generation member is in a non-contact state with said static electricity charging member.
Preferably, during said liquid jetting operation, a distance from said static electricity charging member to said static electricity generation member is longer than a distance from said static electricity charging member to a nozzle forming surface of said liquid jet head.
Preferably, said static electricity charging member and said static electricity generation member are extended in said head scanning direction.
Preferably, said static electricity charging member has a plastic sheet.
Preferably, said static electricity generation member has a brush.
Preferably, said static electricity generation member is driven by power of said feed mechanism.
Preferably, said liquid jet head has a nozzle plate in which said nozzle opening is formed and said nozzle plate is electrically grounded.
According to the liquid jet apparatus by the third aspect of the present invention, liquid drops ejected into an area outside the edges of an object to be processed can be attracted and acquired by using static electricity charged on a static electricity charged member, so that even when liquid drops are to be fed without leaving blanks on the edges of the object to be processed, a liquid mist can be prevented from attaching to the rear edge of the object to be processed and to the inside of the apparatus.